The present invention relates to a guide wire, particularly to a guide wire used to guide a catheter in a body lumen such as a blood vessel.
Guide wires are used to guide a catheter in treatment of cites at which open surgeries are difficult or which require minimal invasiveness to the body such as PTCA (Percutaneous Transluminal Coronary Angioplasty), or in examination such as cardio-angiography. A guide wire used in the PTCA is inserted, with the distal end projecting from the distal end of a balloon catheter, into the vicinity of a target angiostenosis portion together with the balloon catheter, and is operated to guide the distal end portion of the balloon catheter to the target angiostenosis portion.
A guide wire used to insert a balloon catheter into a blood vessel complicatedly bent requires appropriate flexibility, pushability and torque transmission performance (generically called “operationality”) for transmitting an operational force from the proximal end portion to the distal side, and kink resistance (resistance against sharp bending). To meet such requirements, superelastic materials such as a Ni—Ti alloy for improving the flexibility and restoring performance have been desirably used as materials for forming a core member (wire body) of a guide wire.
To select one of branched blood vessels, a distal end portion of a guide wire is often bent into a desired shape by an operator. The operation of bending a distal end portion of a guide wire into a desired shape is called “reshaping”.
In the case of using a wire body made from a superelastic alloy such as a Ni—Ti alloy, however, it is difficult to reshape such a wire body because the wire body has super-elasticity. Accordingly, a reshaping ribbon made from a reshapable material, for example, a stainless steel is required to be additionally provided on the wire body. In this case, since the Ni—Ti alloy used as the material for forming the wire body is poor in wettability against solder, the joining strength of the solder becomes poor, and to enhance the joining strength of the solder, it is required to perform a special treatment of removing an oxide layer on the surface of the Ni—Ti alloy and preliminarily covering the metal surface with tin in a state that the metal is blocked from contacting with air. As a result, it takes a lot of labor and time to produce the wire body made from a Ni—Ti alloy provided with a reshapable ribbon made from a stainless steel.
Conventional guide wires include a core member that is substantially made from a single material. In particular, to enhance the operationality of the guide wire, a material having a relatively high elastic modulus is used as the material of the core member. The guide wire including such a core member, however, has an inconvenience that the distal end portion of the guide wire becomes low in flexibility. On the other hand, if a material having a relatively low elastic modulus is used as the material of the core member for increasing the flexibility of the distal end portion of the guide wire, the operationality of the proximal end portion of the guide wire is degraded. In this way, it has been regarded as difficult to satisfy both requirements associated with the flexibility and operationality by using a core member made from a single material.